Exam 3: Endocrine and Reproductive Systems Flashcards
What is the endocrine system responsible for?
communication and coordination (along with NS)
uses chemical signals called hormones
includes multiple organs spread throughout the body
Nervous system vs. endocrine system
both participate in communication
but differ in their speed and means or signaling
Nervous system:
uses both electrical and chemical signaling, electrical: direct action of electrical potential, chemical: neurotransmitters, very rapid response (milliseconds)
Endocrine system”
uses chemical signaling only, chemical: hormones transported in blood stream, slower response (seconds to days), less specific (may have different effects in different cells)
Both systems are connected: fight or flight response
What are the major organs of the endocrine system?
pituitary gland, adrenal gland, thyroid gland, parathyroid gland, pancreas, pineal gland, thymus, gonads
What are the secondary organs of the endocrine system?
skin, heart, GI tract, kidneys, liver, placenta, adipose tissue
exocrine vs. endocrine glands:
Exocrine: release secretions through ducts, ex: sebaceous and sweat glands of skin, liver (bile), pancreas (digestive juices)
Endocrine: ductless, secrete hormones into surrounding fluid
dense capillary networks or lymphatics pick up hormones and transport them
What are the other local chemical messengers?
Hormones: diffuse into blood or lymph and travel throughout the body
Autocrines: chemicals that elicits response in the same cell that secreted it
Paracrines: induces a response in neighboring cells
What are the two major groups hormones can be divided into?
hormones derived from amino acids
includes amines, peptides, and proteins
hormones derived from lipids
includes steroids
affects hormone distribution and type of receptor is binds to
Explain amine hormones:
synthesized form amino acids tryptophan or tyrosine (amino acid structure modified)
Explain peptide and protein hormones:
differ in amino acid chain
peptide: short chain
amino acid: long chain
synethsized like other body proteins DNA->mRNA->amino acid chain
Peptide: ADH
Protein: growth hormone
Explain steroid hormones:
derived from lipid cholesterol
not soluble in water
must travel bound to transport protein, extends half life of the hormone
ex. testosterone and estrogen
Explain the action of hormones:
hormones bind to a hormone receptor -> protein located inside the cell or within the cell membrane, receptors are specific (recognize hormones with specific shapes and side groups)
Binding of hormone to receptor initates a response
same type of receptor in different tissue may trigger different response (ex. epinephrine)
what are the responses of hormones?
stimulation of protein synthesis
activation/deactivation of enzymes
changes to cell membrane permeability
altered rates of mitosis and cell growth
stimulation of product secretion
What is an intracellular hormone receptor?
receptors located inside the cell
hormones must be able to cross cell membrane
steroid hormones can diffuse through bilayer, thyroid hormones have carrier proteins
binding to receptor creates hormone-receptor complex -> binds to DNA -> triggers transcription of target gene to mRNA, followed by protein synthesis
What is a cell membrane hormone receptor?
receptors located on cell surface
amino acid derived hormones cannot diffuse through bilayer (exception: thyroid hormones)
binding to receptor initates signaling cascade, carried out by secondary messenger, usually cAMP
What is a phosphorylation case in cell membrane hormone receptors?
phosphorylation of proteins can trigger a variety of effects:
changes to nutrient metabolism
synthesis of different hormones and other products
increases efficiency, speed, and specificity or hormonal response
1000s of signaling events can be triggers simultaneously, can respond to low concentrations of hormone in blood stream
signal duration is short -> cAMP is deactivated by enzyme PDE
What is a target cell?
for a target cells to respond to a hormone, it must have specific receptors that the hormone can bind to
target cell activation depends on: blood levels of the hormone, number of receptors for that hormone on or in target cell, affinity if binding between hormone and receptor
What is a large vs reduced hormonal effect?
large: higher hormone levels, more receptors, higher affinity
reduced: lower hormone levels, fewer receptors, lower affinity
How are hormone receptors regulated? up and down
up regulation: low levels of hormone increases the number of receptors for that hormone, cells become more sensitive to hormone
downregulation: high levels of hormone causes decrease in the number of receptors for that hormone, cells become less reactive to excessive hormone levels
how can hormones interact?
two or more hormones can interact to affect response of cells
permissive effect: presence of one hormone allows a another to act
synergistic effect: two hormones with similar effects produce amplified response, two hormones may be required for the cells to respond at all
antagonistic effect: two hormones have opposing effects
what system regulates hormones?
negative feedback systems, some are positive
Manufacture and release of hormones can be triggered by:
humoral stimuli: changing blood levels of ions and nutrients triggers hormone secretion
neural stimuli: nerve fibers stimulate hormone release
hormonal stimuli: endocrine glands release hormones in response to hormones produced by other glands
negative feedback vs. positive feedback:
negative: response is reverse of change detected
postive: response reinforces change detected
what are the secondary endocrine organs?
heart
GI tract
kidneys
skeleton
adipose tissue
thymus
liver
What is sexual reproduction?
combine genes from two parents
union of two gametes to form zygote (fertilized egg), male gametes: sperm, female gametes = egg
sexes typically defined by their sex chromosomes (male XY and female XX)
What are the primary and secondary sex organs in males?
primary: produce gametes-> testes
secondary: necessary for reproduction -> penis, ducts, glands
What is spermatogenesis?
sequence of events that produce male gametes (sperm). starts at puberty, continues daily, ~120 million sperm made daily
What is the site of spermatogenesis?
testes, sperm production occurs in the seminiferous tubules: surrounded by interstitial endocrine cells (leydig cels) -> secrete testosterone into interstitial fluid
What are spermatogenia?
immature germ cells, 2-3 layers on inner surface of semiserious tubules, form from primordial germ cells that migrate into testes during embryonic development
do spermatogenia undergo mitosis?
yes!
type A daughter cells remain to maintain germ line
type B daughter cells migrate towards lumen and are surrounded by nurse cells (Sertoli cells) -> become spermatocytes
What are nurse cells?
aka supporting cells, Sertoli cells
blood-testis barrier: connected by tight junctions of nurse cells, prevents immune system from attacking sperm antigens
support sperm: regulate nutrients, hormones, environmental toxins that can enter tubules, waste removal
Primary and secondary spermatocytes:
primary: undergo meiosis I -> produced 2 haploid cells called secondary spermatocytes -> undergo meiosis II -> produces 4 spermatids with 23 chromosomes in each
What is a spermatid?
not quite sperm cells, small ,round, large nucleus, non-motile
What is spermiogenesis?
spermatids elongate, shed cytoplasm, form tail
now a sperm!
head with flattened nucleus -> genetic storage, acrosome
tail (flagellum) -> locomotor apparatus, mid piece (mitochondria = ATP)
How are sperm stored?
sperm are stored in epididymis and vas deferent (may remain for month, kept inhibited)
How do sperm move?
using flagella
1-4mm/min, movement enhances in neutral-slightly alkaline conditions (semen), increase in temperature will decrease activity, live 1-2 days after ejaculation
Explain abnormal spermatogenesis:
What do the darts and cremaster muscles do?
increase in temperature will decrease spermatogenesis
scrotum maintains testes at lower than body temp
necessary for sperm production
Dartos: smooth muscle that wrinkles skin-> pulls closer to body
Cremaster: skeletal muscles that elevates testes -> pulls closer to body
What does the pampiniform plexus do?
absorbs arterial heat
countercurrent heat exchanger -> blood entering the testes is cooled by blood leaving the testes
What hormones are present in the male reproductive system?
GnRH, FSH, LH and testosterone
What is the HPG axis?
FSH stimulates cells to release androgen-binding protein which keeps high [testosterone] near spermatogenic cells
inhibition: testosterone feeds back to hypothalamus to inhibit GnRh, when sperm count is high, inhibit is released -> inhibits release of GnRH and FSH
What is testosterone?
secreted by Leydig cells in testes
~20% of the mass of testes, increase in number after puberty
What does testosterone do before brith, during puberty and as an adult?
Before brith: masculinizes reproductive tract and external genitalia
Puberty: spermatogenesis, initials growth and development of male reproductive organs, secondary sex characteristics, sex drive, bond growth
Adult: maintain functions initiated in puberty
What are the two phases of the male sexual response?
erection and ejaculation
What is the internal penis?
3 erectile bodies surrounded by dense fibrous connective tissue sheaths
connective tissue and smooth muscle with many bloody sinuses
1 corpus spongiosum surrounds spongy urethra
2 pairs corpora cavernosa
What is an erection?
erectile tissue fills with blood
when not aroused: arterioles supplying erectile tissue are not constricted
during sexual excitement, PNS releases NO
NO activates enzymes that form cGMP which causes vasodilation of penile arteries-> expansion of erectile tissue compresses drainage veins
What is erectile dysfunction?
inability to attain an erection, due to deficient release of NO
can be caused by: psychological factors, alcohol, antidepressants and other drugs, chronic conditions
may be treated with drugs like viagra which will blood PDE5-> and enzyme that breaks down cGMP
cGMP regulates blood flow to penis -> more cGMP = more blood flow
What is the male duct system?
sperm are made in the testes but must edit the body in semen for reproduction to occur, has accessory ducts
What are the 4 accessory ducts:
Epididymis: coiled ducts that contract to expel sperm, sperm storage, maturation (20 days) and norushiment
Ductus Vas Deferens: muscular duct travels through spermatic cord, joins with the….
Ejaculatory duct: travels through prostate and empties into the….
urethra: secreted lubriatcting mucus, shared between sperm and urine
What are the accessory glands?
seminal vesicles
prostate
Bulbo-urethral glands
seminal vesicles (2): contract during ejaculation
yellowish viscous alkaline fluid (70% of semen), fructose for ATP production, enhances sperm motility and fertilizing capability, joins with dutus deferent to form ejactulatory duct
Prostate: encircles urethra, milk, slightly acidic fluid (30% of semen)
Bulbo (2): secretes before ejaculation, thick, clear mucus (not part of semen), lubriactes spongy urethra and glans penis, neutralizes traces of urine
What is semen?
milky, white alkaline fluid
ph: 7.2-8.0
sperm/acessory gland secretions
function: transport medium for sperm
~2-5 mL/ejaculation with 100+ million spermW
What is ejaculation?
occurs when sexual stimulus becomes intense
SNS impulses exit spinal cord -> emission: vas deferens contract (pushes sperm into internal urethra), prostate gland and seminal vesicles contract (expel prostatic and seminal fluid, mixes with sperm)
filling of internal urethra sends signals to spinal cord -> leads to rhythmic contractions or muscles that compress that base of the erectile tissues -> wave like contractions forces semen from the urethra -> propelled at 11 mph
What is the refractory period?
occurs after ejaculation, the time during which it is impossible for a man to have additional orgasams, may be causes by oxytocin released during orgasam, increases with age
oogenesis vs spermqtaigenis table
review table + meiosis differences
What is oogenesis:
production of female gametes (occurs in ovaries, meiosis), takes years to complete (begins during fetal period and become active after puberty), cynical events (hormones, ovarian and uterine histological changes, uterine changes - menstrual flow, completed until menopause)
What are the 2 areas of the ovaries?
cortex- forming gametes
medulla- blood vessels and nervesW
What are ovaries: follicles?
tiny sac like structures in the cortex, contain oocytes (immature eggs)
follicles go through development and change in complexity
if there is one layer of cells around the follicle : cells are follicle cells
If more than one layer is present: granulosa cells
Explain oogenesis in the fetus:
oogonia (2n) multiple via mitosis until month 5 (6-7 million)
primary oocytes develop in primordial follicles (begins mitosis I before birth; stalls in prophase I, most degenerate by birth (1-2 million left)
female infants have a lifetime supply of primary oocytes E
Explain oogenesis after puberty:
~200,000 remain at puberty, 20-25 primary oocytes activated monthly (most degenerate, one is “selected” -> dominate follicle containing oocyte -> resumes meiosis I)
primary oocyte in dominant follicle finishes meiosis I -> 2n daughter cakes
secondary oocyte: large, has most of mother cell’s cytoplasm and organelles
first polar body: small, mostly devoid cytoplasm
secondary oocyte stalls in metaphase II -> destined to be ovulated,
if not penetrated by sperm -> deteriorates
if penetrated, completed meiosis II
zygote and second polar body
What is down syndrome?
caused by an extra copy of chromosome 21 (trisomy 21), maternal age is an important factor is the frequent of trisomy
What is the ovarian cycle?
monthly series of events that matures an egg, may happen ~500 times throughout life
What are the phases of the ovarian cycle?
Follicular phase (days 1-14) - mature vesicular follicle grows
ovulation occurs mid-cycle
Luteal phase (days 14-28) - corps luteum activity
What are the stages of the follicular phase?
- primordial follicle
rising levels of FSH stimulation activation of follicles, Midway through follicular phase, FSH drops -> one follice becomes dominant follice and continues to grow, remaining follicles disintegrate - Primary follicle
- Secondary follicle
- Tertiary follicle
- Mature vesicular follicle
What is ovulation?
ovary wall ruptures and expels the secondary oocyte, 1-2% of ovulations release >1 secondary oocyte
What occurs in the luteal phase?
ruptured follicle collapses -> granulosa cells and internal theca cells from corpus luteum -> secretes progesterone and estrogen -> stimulates the thickening of the uterine wall
If pregnancy occurs: corpus luteum produces hormones until the placenta takes over at about 3 months
If no pregnancy, the corpus luteum degenerates into a corpus albicans in 10 days
How is the ovarian cycle hormonal regulated?
hypothalamus releases GnRH -> anterior pituitary releases FSH and LH -> in the ovaries, follicles grow, mature, secrete estrogen -> low levels of estrogen being secreted by follicle inhibits FSH and LH
Dominant follicle released constant level of estrogen -> anterior pituitary -> LH surge just before ovulation -> oocyte completes meiosis I -> ovulation1 -> ruptured follicle -> corpus luteum -> inhibits FSH/LH again
How does the corpus luteum play a role in hormonal regulation of the ovarian cycle?
Corpus lutem-> progesteron, estrogeen, inhibin
anterior pituitary and hypothalamus -> inhibits FSH and LH -> prevents other follicles from maturing -> prevents other oocytes from being ovulated
uterus -> cervical mucus thickens -> preps endometrium for pregnancy
What is the pathway of the secondary oocyte? simple
ovulated secondary oocyte exits ovary -> enters peritoneal cavity -> then….uterine tubes!
What are the uterine tubes?
+ components
AKA fallopian tubes, secondary oocyte passed through to uterus
isthmus: where UT empties into uterus
ampulla: widened area
infundibulum: funnel-shaped and ciliated
fimbriae: finger-like projections sweep ovum in
What is the pathway of the secondary oocyte continued?
enters uterine tube and progress to uterus (3-4 day journey)
for fertilization to occur, secondary oocyte must be penetrated by sperm within 12-24 hours after ovulation (meiosis II occurs here, uterine tubes)
What is the uterus?
thick, muscular walls (nourished embryo/fetus), size and shape of inverted pear
What are the 3 layers of the uterine wall?
perimetrium (outer): serous membrane
myometrium (middle): smooth muscle contracts to expel fetus
endometrium (inner): mucosal lining, simple columnar epithelium over a thick lamina propria, where embryo implants, 2 layers: functional and basal
What is the uterine cycle = menstrual cycle?
purpose and interruptions
begins at puberty (~11-12 years old), cycle length = 21-35 days, continues until menopause, interruptions: pregnancy, illness, stress, starvation
purpose: prepare uterus for possible embryo implantation
What are the 4 phases associated with the endometrium?
menstrual phase (1-5): endometrial functional layer is shed
proliferative phase (6-14): functional layer is regenerated
secretory phase (15-26): thickening due to secretion and fluid accumulation rather than mitosis, cervical plug forms (keeps uterus private)
premenstrual phase (27-28): AKA ischemic phase, brings on tissue necrosis
changes directed by ovarian hormone levels of estrogen and progesterone
explain the two layers of the endometrium and what they do:
Functional layer: cycles in response to hormones, shed during menstartion
Basal layer: reforms functional layer after menstruation ends, proliferative phase of uterine cycle
explain endometrial blood flow:
uterine artery -> arcuate arteries -> straight arteries -> spinal arteries
Spinal arteries constrict and spasm causing shedding of functional layer
degenerate and regenerate monthly, menstruation lasts 5-7 says (30-50mL of blood lost)
High levels of ——- are responsible for the LH/FSH surge that promotes ovulation whereas low ——– inhibits LH/FSH
estrogen
what is the vagina and its function?
thin walled distensible tube, 3-4 inches long, extends from cervix to exterior, acidic = reduces bacteria
function: passageway; menstrual flow, copulation, delivery of infant
What is the female sexual response?
similar to male
PNS activity analogues to erectile phase in males
Engorgment of: labia, clitoris, vaginal transudate, bulbs of vestibule, breasts, uterine tenting effect, vestibular glands secrete lubriacting mucus
SNS implies discharge also analogous, but with no ejaculation. Muscular/uterine contractions associated with intense plessure
What are the different ways to prevent pregnancy? 4
condoms/ vasectomy: prevent sperm from reaching vagina
birth control pills: constant level of estrogen and progesterone inhibits release of FSH and LH -> prevents ovulation. Placebo pills cause a decline in hormones, triggering menses
IUDs: may contain levonorgestrel -> inhibits release of FSH and LH -> prevents ovulation
Plan B: contains levonorgestrel
What is the journey of the sperm to the egg?
ejaculation releases hundreds of millions of sperm
must overcome: vaginal acidity (pH 3.8), cervical mucus, uterine leukocytes
only a few hundred thousand make it to the uterine tubes
What is capacitation?
fluids in the female reproductive tract prepare sprem for fertilization, must undergo this process in order to penetrate egg
improve motility
thin membrane of the sperm head
How does the sperm contact the oocyte?
corona radiata: granulosa cells form oocyte development, secrete chemical attractants for sperm
sperm burrow through corona radiatia, bind to receptors in zone pellucida
acrosomal reaction: enzymes released from the acrosome all sperm ti reach oocyte
sperm contacts sperm-binding receptors on oocyte
plasma membrane fuses with oocytes membrane
How is polyspermy prevented?
only one sperm cell and fertilize an oocyte
when sperm first binds to plasma membrane:
fast block: change in sodium ion permeability -> prevents further sperm from fusing
slow block: granules beneath plasma membrane release inhibiting proteins -> release other attached sperm, destroy sperm receptors, mucopolysaccharides create barrier called fertilization membrane
What occurs prior to and after fertilization?
Prior: oocyte arrested in metaphase II, once fertilizes, meiosis is completed, genetic material intermingles, resulting in a diploid zygote
mitosis causes growth of zygote
at ~70-100 cells, called a blastocyst
blastocyst adheres to uterine wall -> begins implantation
What is implantation?
blastocyst embed in uterine lining (50-75% of blastocyst fail to implant)
blastocyst digests uterine wall -> mucosa rebuilds itself, surrounding the blastocyst
hCG is secreted -> directed corpus luteum to survive -> continues to produce progesterone and estrogen
hCG is detectable in urine (at home pregnancy tests)
How do endocrine organs play a role in pregnancy?
for the first 7-12 weeks, hormones are primarily secreted by the corpus luteum
progesterone stimulates production of cells that nourish the blastocyst before the placenta
during weeks 12-17, the placenta takes over ->
corpus luteum degenerates, convertes hormones secreted by maternal and detal adrenal glands to estrogens-> estrogen levels increases 30X by childbirth
What is the role of estrogens?
Suppress FSH and LH
induce growth of fetal tissues
maturation of fetal lungs and liver
regulate progesterone production
triggers fetal synthesis of cortisol (maturation of lungs, liver, and endocrine organs)
stimulate maternal tissue growth (uterus and mammary glands)W
What are the other hormones secreted by luteum and then the placenta?
Relaxin: increases elasticity of pubic symphysis and pelvic ligaments -> dilates cervix during labor
Progesterone: supresses FSH and LH -> inhibits uterine contractions, levels drop in late gestation
hCG: stimulates male detal gonads to secrete testosterone, essential for development of male reproductive system
What are the other hormones secreted by the anterior pituitary in pregnancy? And the parathyroid?
Thyrotropin: increases production of thyroid hormone, increases maternal metabolic rate -> increases appetite and causes hot flashes
Prolactin: enlargement of mammary glands
ACTH: stimulates protein synthesis via cortisol
Parathryoid:
Parathyroid hormone: mobilizes free calcium for fetal use
Which hormones are active in labor and what do they do?
progesterone levels plateau and then drop around month 7
increasing estrogen:progesterone ratio makes smooth muscle of uterus more sensitive
at ~8 months, fetal cortisol rises -> further boost estrogen secretion
Near labor, posterior pituitary secretes more oxytocin -> stimulates contractions and release of prostaglandins (also stimulates contractions), artificial version of these hormones can induce labor
What is sex determination?
sex chromosomes X and Y. XX=female and XY=male , variations do exist
Gametes from mother- always contain X chromosome
Gametes from father- 50% X 50% Y, determines sex of offspring
What is the Y chromosome?
single gene that initiates testes development
SRY
without SRY, embryos develop as females
What is nondisjunction?
can lead to aneuploidy - more or less than 2 copies of each chromosome
Typical development aneuploidy:
Genotype: XX or XY
Phenotype: Female (XX) or male (XY)
How does differentiation of the reproductive system occur?
male and female embryos being with the same structures, sexually indifferent stage, contain bipotenital tissues
What are biopotential tissues?
cells that develop into either male or female gonads
testosterone can influence biopotential tissues t0 become male reproductive structures
What are non-biopotential tissues?
Two duct systems
internal reproductive structures: uterus/ uterine tubes/ portions of vagina, epididymis/ ductus deferens/seminal vesicles
form from one of two duct systems:
female ducts: Mullerian duct
Male ducts: Wolffian duct
What is the gonadal ridge?
begin development during week 5
primordial germ cells migrate here, will become spermatogonia or oogonia
gonadal ridges then form tests or ovaries
Explain male internal developement:
SRY gene creates testes determining factor (TDF) -> gonadal ridge develops into testes
testes produce: MIF -> causes degeneration of Müllerian duct
testosterone: promotes development of male sex characteristics
Explain female internal development:
No SRY gene -> absence of TDF
Gonadal ridge develops into ovaries
ovaries do not produce MIF or testosterone
No MIF-> mullerian duct develops
no testosterone: wolffian duct degenerates
What does external genitalia arise from?
genital tubercle, depends on presence or absence of testosterone
What is puberty?
individuals become sexually mature, results from development of secondary sex characteristics
Explain the hormonal control of puberty:
age 8-9
approaching
onset
hypothalamus secretes GnRH, anterior pituitary secretes LH and FSH, gonads secrete testosterone or estrogen
age 8-9: LH productions become detectable, negative feedback system is very sensitive
low concentrations of androgens or estrogens inhibits hypothalamus and pituitary. GnRH, LH, and FSH production low
Approaching: sensitivity of negative feedback decreases. gonads increase in sensitivity to FSH and LH, as a result, levels of LH and FSH increase and lead to maturation of gonads -> leads to secretion of higher levels of sex hormones
Onset: may be influenced by nutrition, may be a link between puberty onset and amount of stored fat
more pronounced in girls, may reflect metabolic costs of gestation and lactation, in lean ,active women, there’s often a delay in the onset
Puberty in females:
Growth of breast tissues, growth of axillary and pubic hair, growth spurt ~9-11,
menarche (start of menstruation)
Puberty in males:
Growth of testes, followed by growth and pigmentation of scrotum and growth of penis, growth of armpit, pubic, chest, and facial hair, testosterone stimulates growth of larynx and thickening/lengthening of vocal cords, ejaculation with sperm at ~15 years, growth spurt at ~11-13, development may occur through early 20s
What is menopause?
Ovaries become less responsive to gonadotropin signals
§ Estrogen production declines
§ Ovarian cycles may release 0 to 2+ oocytes
§ Menstrual periods become erratic and shorter
Menopause:
§ Ovulation and menstruation cease
§ Occurs between ages of 46 and 54
§ Estrogen production eventually ceases
What are the effects of a lack of estrogen?
Atrophy of reproductive organs and breasts, vaginal dryness, irritability
and depression, vasodilation of skin’s blood vessels (hot flashes), loss of
bone mass
o May be treated by low doses of estrogen
§ Hormone replacement therapy (HRT), controversial: may increase risk of heart disease, breast cancer, stroke, and dementia
Is there an equivalent to menopause in men?
No equivalent in men, but:
§ Testosterone production does decrease, refractory period after orgasm
increases, sperm motility decreases
§ May be treated testosterone replacement therapy
